How Does a Prism Create a Rainbow?
By Enoch K

A prism creates a rainbow by having light pass through it. When the light passes through the prism, the light refracts and separates making the colors of the visible spectrum. A prism is basically doing what raindrops do in the sky to create rainbows. In 1665, Isaac Newton discovered that, if light goes through a prism, it separates into the visible spectrum.

What is a Prism?
A prism is a piece of see through material that has at least four sides called faces. Prisms are also geometric shapes. The most common shape for a prism is the triangular prism. Triangular prisms have five faces. Although the triangular prism, is the most most commonly seen, prism can have four faces to infinity. Prisms can be made in different shapes and sizes, but the main purpose of a prism is to bend light.
This is a triangular prism.

The Visible Spectrum
The visible spectrum is the called the visible spectrum because it is the onlt part of the electromagnetic spectrum that we can see. The colors of the visible spectrum are, red, orange, yellow, green, blue, indigo, and violet. The electromagnetic spectrum is a wide range of light that goes from gamma waves to radio waves.
This is the electromagnetic spectrum.

Refraction is what "makes" the rainbow when light goes through a prism. Refraction is basically light bending. When light enters a prism, the different colors bend at different angles, therefore, you can see all the colors of the visible spectrum. Why does this happen? The colors of the visible spectrum travel at different speeds. Red is the fastest color, so it bends the least. Violet is the slowest color, so it bends the most. Here’s a fun fact about the refraction of light. If you bend light with one prism it separates the light to make the visible spectrum, but if you use a prism on the already separated visible spectrum, it combines all the colors to make regular light. Here is a diagram to help you understand the refraction of light.
This is my diagram showing what happens when light goes through a prism.

Rainbows in the Real World
In the real world, rainbows are formed by sun light passing through raindrops. Raindrops act like prisms and they refract the sun light. Each individual raindrop refracts the sun light a different direction. When you observe a rainbow in the sky, you will probably see the most vibrant, single rainbow. Some times, you’ll see the less-common partial-double-rainbow. And sometimes, on rare occasions, you’ll see the least-common, double-rainbow that goes all the way.
Refract- To refract is to alter or distort.
Spectrum-A continuous sequence or range (of light).
Electromagnetic Spectrum- The electromagnetic is the range of light. It goes from the shortest, gamma rays, to the longest, radio waves.
Gamma Ray-A photon that is emitted from a radioactive substance.

Lowe, Lindsey, ed. Light and Sound. Tucson: Brown Bear Book Limited, 2010. Print.

"Prism." Britannica Elementary Encyclopedia. Encyclopædia Britannica Online School Edition. Encyclopædia Britannica, Inc.,2011. Web. 15 Sept.2011.

Refracted Light. Prod. Colgren Communications., 2004. Discovery Education. Web. 13 September 2011. <>.